The German unexamined laid-open patent application DE 100 59 854 A1 discloses a thermographic test method in which a specimen surface is excited by the transfer of ultrasound thereto and then evaluated by means of a thermal imaging camera. When ultrasound is transferred to a defective component, the ultrasonic energy is preferentially converted to heat at the defective locations.
Finding cracks in ceramic nozzles has been found to be problematic in the prior art. Usually, an experienced quality assurance representative uses a small hammer to tap on ceramic nozzles, which always comprise at least one cavity. The sound resulting when the nozzles are tapped on then serves as an indication of cracks and/or defects that may exist in the nozzles. The examination of ceramic nozzles by means of automated, mechanical processes poses great problems, since nozzles composed of ceramic or ceramic-like materials are fragile under conditions of exposure to severe mechanical and/or thermal stresses.